Trim Question...BC vs Dry Suit??

[DiveMaven]

I currently do not dive dry, so don't know a lot about it...which is why I'm asking you guys. A friend of mine was telling me how it's better to control your bouyancy and trim by putting air in your dry suit instead of your BC. That doesn't seem right to me since the air can move from neck to ankles freely in the dry suit, and completely throw the diver off. It seems safer to use the BC for that.

Opinions please!

 

[jagfish]

Oooh, I don't know...

In my own case I find that if I have more than minimal air in my suit, I tend to get foot light, which dogs my trim...

 

[Jason B]

wing is for buoyancy and drysuit is for warmth.

Jason

 

[H2Andy]

i'm a brand new dry suit user, but it seems to me that using the drysuit as
an inflation device is too cumbersome. there's too many extremeties for the
air to go into and play tricks on you, and also, it vents so slowly that you
can't realy control your bouyancy with it efficiently.

 

[jonnythan]

i'm a brand new dry suit user, but it seems to me that using the drysuit as
an inflation device is too cumbersome. there's too many extremeties for the
air to go into and play tricks on you, and also, it vents so slowly that you
can't realy control your bouyancy with it efficiently.

But it's too difficult to manage two separate air spaces underwater.

The SSI Dry Suit Diving book actually states that.

Me, I think it's too difficult *not* to. Having any more air than absolutely necessary throws off my trim, and it's darn near impossible to keep that air where I want it. Always ends up in my feet or trapped behind my shoulders. Keep the squeeze on, keep the air in the BC and out of the drysuit.

 

[Web Monkey]

Using a drysuit for buoyancy is like using a BC with a hole in it.

Since a drysuit will vent any time the exhaust valve gets above the air-bubble (unless you have the valve cranked shut), you'll lose your mind trying to keep air in it.

Just add anough air so the water isn't crushing you and the underwear, and use your BC for buoyancy. You can't get floaty feet if there's hardly any air in the suit.

Terry

I currently do not dive dry, so don't know a lot about it...which is why I'm asking you guys. A friend of mine was telling me how it's better to control your bouyancy and trim by putting air in your dry suit instead of your BC. That doesn't seem right to me since the air can move from neck to ankles freely in the dry suit, and completely throw the diver off. It seems safer to use the BC for that.

Opinions please!

 

[doole]

I agree with the rest of these guys: I've always thought that using a drysuit for bouyancy was a bit like trying to use a BC to stay dry; not the intended function of the tool.

 

[MXGratefulDiver]

I used a drysuit for buoyancy successfully for a long time ... because that's how I was taught to do it. It can be done ... and it's commonly how manufacturers recommend it, and how instructors teach it.

However, using the BCD (or wing) for buoyancy is more efficient ... for all the reasons listed above. The air shifts around less, it shifts in a more confined space, and it doesn't vent unless you want it to.

FWIW - managing two air sources is a complete non-issue if your drysuit dump valve is properly adjusted ... when you raise your BCD inflator hose to vent, the drysuit valve will also vent in the same motion, and proportional to the pressure exerted on it based on your depth. That's why drysuit manufacturers (unless you request otherwise) place the dump valve on your left shoulder.

... Bob (Grateful Diver)

 

[String]

This thread could turn ugly. Use the search, DS buoyancy method is a common topic.

My view:- single cylinder correctly weighted diver can use either without problems.

 

[Doc Intrepid]

<snipped>...it vents so slowly that you
can't really control your bouyancy with it efficiently.

...the majority of the respondents appear to be in violent agreement!

The point Andy makes above, however, is (IMHO) one of the most important points for new drysuit divers to understand. A BC (or wing - whatever) is a fairly cohesive bubble and it can be dumped relatively rapidly by most divers. A drysuit is not - it has arms and legs, straps and fasteners, etc. that can trap gas. As Andy noted a drysuit valve is not designed to 'dump' a drysuit rapidly (particularly if the diver has gotten inverted/feet up, or is horizontal or some version thereof). In the event the drysuit "gets away from you", or IOW you're rising faster than you can dump the gas from the suit because the gas in the suit keeps expanding, it can ruin your entire day.

For most drysuit users this isn't a problem - most have learned to dive under control. For a new drysuit diver or a diver who lacks control this can be a real challenge to diving dry.